From: David Edelsohn <dje@watson.ibm.com>
To: Roger Sayle <roger@www.eyesopen.com>
Cc: gcc@gcc.gnu.org
Subject: Re: Strange conditional jumps on the POWER4
Date: Sun, 06 Apr 2003 03:33:00 -0000 [thread overview]
Message-ID: <200304060211.VAA31048@makai.watson.ibm.com> (raw)
In-Reply-To: Message from Roger Sayle <roger@www.eyesopen.com> of "Sat, 05 Apr 2003 14:38:03 MST." <Pine.LNX.4.44.0304051355450.14942-100000@www.eyesopen.com>
>>>>> Roger Sayle writes:
Roger> but the same code, (j > 1), generates with gcc3.4 "-O2" (600 ticks)
Roger> L..10:
Roger> cmpwi 7,31,1
Roger> li 31,1
Roger> ble- 7,L..4
Roger> li 31,0
Roger> L..4:
Roger> bdnz L..10
Roger> However, with (j == 1) and "gcc-3.4 -O2 -fno-if-conversion", we get
Roger> (1200 ticks)
Roger> L..10:
Roger> cmpwi 7,31,1
Roger> li 31,1
Roger> beq- 7,L..12
Roger> bdnz L..10
Roger> L..13:
It appears that you are not compiling the code with -mcpu=power4
commandline option for GCC 3.4, because the branch hint mnemonics (+/-)
would not be present without greater probabilities.
David
next prev parent reply other threads:[~2003-04-06 2:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-05 21:26 Roger Sayle
2003-04-06 1:42 ` Zack Weinberg
2003-04-06 1:59 ` Roger Sayle
2003-04-06 3:33 ` David Edelsohn [this message]
2003-04-06 5:21 ` Roger Sayle
2003-04-06 16:49 ` Segher Boessenkool
2003-04-07 23:03 ` David Edelsohn
2003-04-06 15:14 ` David Edelsohn
[not found] <200304080131.VAA30506@makai.watson.ibm.com>
2003-04-08 15:50 ` Roger Sayle
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